Servo system testing



Feb. 14, 1950 R. A. CARPENTER ETAL 2,497,069

SERVO SYSTEM TESTING Filed Jan. 15, 1946 AN TENN A :E I E; l

l3 0.8.0. [111m I I2 MOTOR MOTOR 7 3 It SYNCHRO i In Illlllllllh I If H MOTOR AC Q 2 CONTROL 4 RECTIFIER \DIFFERENTIAL SYNGHRO GENERATOR GENERATOR I us v Ac CONTROL AMPLIFIER MOTOR 'Q I 1 l 4| 4O CONTROL SYNCHRO TRANSFORMER GENERATOR 2| 22 I 0.0. MECHANICAL DRIVE MOTOR DIFFERENTIAL REVOLUTION COUNTER 23 SPEED ADJUSTMENT REVERSING SUPPLY SPEED D c REVOLUTION SWITCH ADJUSTMENT MOTOR COUNTER SUPPLY Patented Feb. 14, 1950 SERVO SYSTEM TESTING I Ralph A. Carpenter and Donald M. Lowe,

Washington, D. 0.

Application January 15, 1946, Serial No. 641,362

. v Claims. (01. 73-1) (Granted under the act of March 3, 1883, an

Automatic control has a wide variety of applications. Servo systems are useful on ships, for instance, in connection with antenna drive systems, and fire control director systems for moving guns in train and elevation to bring them on a target. In such an installation, an antenna or gun might be required to take on a rotary motion, an oscillatory motion, or some combination of these motions. 1

In order to test the operation of a control system or units thereof in the laboratory, it is desirable to simulate the mechanical or electrical inputs received in the actual installation. Furthermore, a portable servo test unit would be useful for imparting such signals. or movements to the units of a shipboard installation, for some parts of the system may. be inoperative or operative with diiiiculty at the time the test is to be made.

It is an object of the invention to provide continuous or oscillatory rotational movements for testing automatic control systems.

It is another object of the invention to provide a mechanical movement to test the effectiveness of servomotors or generators, or servo or control amplifiers, or antenna driving systems. I l The invention will be further understood with reference to the drawing in which:

Fig. 1 shows in block diagram an exemplary antenna control system in connection with the testing of which the invention may be employed.

Fig. 2 shows in block diagram an exemplary embodiment of the invention.

In the control system of Fig. 1, the antenna is caused to move in response to the rotation of a slewing motor or hand crank plus the ships changes of course. The motion of motor I or of hand crank '2 is communicated through gear 3 and shaft 4 to the rotor of synchro generator 5. The rotor is a coil free to rotate inside a fixed stator coil, the rotor being energized by the ships A.-C. supply. The motion of the rotor of generator 5 causes an electrical signal to be induced in the windings of the stator, which signal is communicated' to the stator "of the difierential generatorv 6. A voltage is thus induced in the rotor of the differential generator which depends on the motion of the hand crank or slewing motor. The rotor of the difierential generator 6 is rotated in response to the ships change of course by motor I. when the rotor of 6 moves due to a amended April 30, 1928; 370 O. G. 757) the signal in the stator change in phase andamplitude. Hence, the voltages in the rotor depend on the combined motions of the slewing motor or hand crank and the change in course.

These voltages appearing at the stator of con-. trol transformer l0 result in an error voltage appearing in its rotor depending. upon its position relative to the rotors of generators 5 and 6. This error signal isemployed by control rectifier ll-to energize the antenna driving motor I2, which rotates the antenna through gear [3 and shaft I l. The motion of the antenna is fed back through shaft I5 and gear IE to, drive the rotor of control transformer it toward the position of no error signal. I v

Therefore, if the hand crank is turned slightly or'the ship makes a small change of course, a small error signal is produced in the rotor of the control transformer Ill due to the sum of the motions. The antenna will be driven until the control transformer rotor is moved back to the no error signal position, the antenna thus taking on the combined motion of the hand crank and the ships change of course. If the slewing motor or hand crank is moved continuously and the ship constantly changes course, the antenna will move continuously in response to these movements. The antenna might be given, for example, a combination of a continuous and oscillatory rotational motion, if the ship steers a zigzag course while the slewing motor I rotates continuously.

The exemplary embodiment of the invention shown in Fig. 2 is a device used in testing auto-' matic control systems, of which the system of Fig. 1 is merely one typical example. The inven-' tion imparts movements to'such a system simulating those occurring in an actual installation.

A D.-C. drive motor 21 imparts a rotary motion through a gearreduction to the spider of mechanical differential 22. The speed of this motion can be varied by a potentio-meter or other speed adjusting device 23. The direction of rotation can be changed by the reversing switch 24.

The rotary motion of motor 25 is changed to an oscillatory'motion about a fixed axis by reciprocating mechanism 26. The speed of motor 25 may be adjusted by control 21. The movement of the motor is ordinarily appliedthrough a gear reduction to the reciprocating mechanism. Motors 2| and 25 may be provided'with revolution counters 30 and 3|.

The reciprocating mechanism 26 consists of two wheels 33 and 34 with a connecting rod 35 chance of course, the voltages induced in it by attached to the eccentrics 36 and 31. The resulting motion given the differential 22 by the mechanism 26 is approximately simple harmonic. Its period depends on the speed of the motor and its amplitude on the relative radii of the two eccentrics. The wheels are drilled with a series of holes in order that the shaft may be attached at each of its ends atvarying dfstanbesjrom the centers of the wheels. Other devices known to the art for producing oscillatory movements may be used instead of mechanism 26.

The simple harmonic motion of mechanism 26 is applied to differential means2 2, where it is combined with the rotary motion from motor i2l to produce the resultant of the two motions. It is to be understood, however, that-in "some appli cations, the motions might be combined electrically rather than mechanically.

The resultant motion referred to in the above paragraph is an oscillatory rotational movement. The variable rotation of the differential output shaft may or may not involve actual reversal of the shaft depending on the relative speeds of the two'motors 2| and'2'5. Moreover, if-m'otor '21 only is energized, rotation at uniform angular velocity results. If motor :25 only is energized the resultant is oscillatory motion only.

As shown in Fig. 2, the output of differential 22 is applied to the synchro system to be tested. Such a system, for "simplicity, has been shown as comprising only a synchro generator 40, a 'eontrol transformer 4 l, a oontrolam'pl-ifier 12-, a motor 43, and a load 44. The resultant motion of differential 22 is applied to the rotor of synchro generator 40, causing an electrical 'signal to appear in the stator windings. This electrical signal, fed to the-comm transformer f, results "in'an error voltageo'utput der'u'ahde'nt"on the relative positions of the generator -Ml rotor and the "control transformer 4| rotor. Since the control transformer rotor is positioned by'a feed back shaft and gearing from the load 44, this error signal 'dependson the misalignment of the load and the difierer'itia'l 22 outputsha'ft. The error voltage is fed from the control transformer to the control amplifier 42, which furnishes current to motor '43 to drive the load M to corres'pfo sh e with thedifferential 22 output shaft. 7 The system is so arranged that the load follows closely the outpu'tmotion'of the differential. I

In certain applications the synchro generator 40 might be a component "of the test itself. For other applications, other synchro unit'smight replace the synchro generator.

By "use of suitable measuring devices knows 'to the art, such as a cathoderay oscilloscope fed by the error voltage of the system, various duan'ti ties which give anfindication of system '"orunit Performance can bedetermined.

7 While but one embodiment of this invention has been shown and described, it will be understood that many changes and modifications may be made therein without departing from the spirit orscope of the present invention. u

The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

What is claimed is:

-1. A test device for aservo control system which 4 includes a synchro generator comprising two variable speed motors, a differential coupled to one of said motors driving the synchro generator, oscillatory means coupled to the other motor operative to change the rotary motion thereof to a. substantially simple harmonic motion, and means coupling the oscillatory "means to the differential means.

A test device for a servo control system which includes a synchro generator comprising differential means including a plurality of input means and an output means, means coupling the output means of said differential means to said synchro generator, motor means applying a rotational motion to one of said input means and oscillatory means applying a simple harmonic motion to another of said input means.

3.;A test device for a servo control system which includes a synchro generator comprising differential means including a plurality of input means and 'outputmearis, means coupling said output means to said synchro generator, motor means applying a rotational motion to one of said input means, oscillatory means applying a simple harmonic motion 'to another'of said input means, mo'tor controlled m ans for varying the rates: said rotational motion and control means for varying the amplitude and period of said simple harmonic motion. I

4. A test device for a servo control system which includes a synchro generator comprising differential means including a pluralityof input means and an output means, means coupling said output means to said synchro generator, motor means applying a rotational motion to one of said input means, oscillatory means applying a simple harmonic motion to another of said input means, motor control means for determining the rate and direction or said rotational motion and control means for determining the amplitude and period of said simple harmonic motion.

5. In combination, a synchro generator having input and output means, differential means including a plurality of input means and anoutput means, means coupling the output means of said diiferentialhieans'to theinp'ut means of said synchro generator, motor means applying a rotational motion 'to one of said differential input means and oscillatory means applying 'a simple harmonic moti'o'r'i to "another or said differential input means.

RALPH CARPENTER.

LOWE.

REFERENCES CITED The following references are or record in the file 'of this patent:

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